An Experimental Study on the Capillary Tube Flow and its Effect on the Acoustic Behavior of Household Refrigerators

The aim of this work was to study the relationship between capillary tube flow and the acoustic behavior of household refrigerators by investigating a particular type of fluid-induced noise, known as fluctuating noise. To this end a household refrigerator was carefully instrumented and firstly tested in a reverberant chamber and secondly in a climate-controlled chamber. Acceleration measurements were taken at the evaporator inlet pipe showing that the refrigerant flow in that region was highly pulsating. Visualization of the flow pattern at the inlet of the capillary tube was also carried out and revealed the presence of vapor bubbles for most of the time. A needle valve was then installed in series with the freezer capillary tube in order to increase the restriction and match the compressor and the capillary tube mass flow rates. The restriction provided by the optimum needle valve-capillary tube pair was then converted into an equivalent capillary tube. It was found that the higher-restriction capillary tube attenuated the pulsating characteristic of the refrigerant flow, almost completely attenuating the disturbing fluctuating noise.